Multiple-hearth calcining furnace



Jame 26, 192.

R. D. PIKE MULTIPLE HEARTH CALCINING FURNACE Filed Nov. 19, 1925 2 Sheets-Sheet 11111 I e v June 26, 1928, 11,674,919

R. D. PIKE MULTIPLE HEARTH CALCINING FURNACE Filed Nov. 19, 1923 2 sheets-sheet 2 Patented June 2%,

JRQBERT D. PIKE, OF SAN FRANCISCO, CALIFORNIA.

BE'ULTELEl-HEARTH CALCINING FURNACE.

' Application filed November 19, 1&23. Serial No. 675,448.

The hereinafter described invention re lates in general to the construction of the principal combustion hearth of multiple calcining furnaces and more particularly to that type of calcining furnace wherein the combustion hearth is the lowermost one and in the region of which a very high temperature is carried due to the fact that all of the fuel is injected over said hearth. Where all m of the fuel is burned immediately over the principal or lowermost hearth of the furnace, an intense flame will result with ultimate damage to the brick work or result in an overfiring of the material under treatp ment. To eliminate this difliculty, and at the same time to burn the necessary amount of fuel, I provide by the present invention control means for decreasing the air supply in the region immediately adjacent to the an injected fuehthereby cooling the flame at this point by reasonof the consequent incomplete combustion, while arranging for the introduction of the balance of the air for combustion in a zone farther along the path of the flame. This latter air causes combustion of the combustible products which result from the initial incomplete combustion of the fuel and causes a secondary flame, which is long, not intense in its nature. At the same time 1 cause the air for the secondary combustion to pass through channels or passageways in the brick work which enclose the principal combustion chamber, which results in a cooling of and a prolonging of its life. To comprehend the invention, reference should be had to the accompanyin sheet of drawings, wherein- Fig. 1 is a roken vertical sectional eleva tion of the apparatus with my invention applied thereto.

Fig. 2 is a cross sectional plan view taken on the line 2-2, Fig. 1 of the drawings.

In the drawings the letter A is used to designate any suitably constructed calcining furnace which is provide centrally with a vertically disposed rotating column consisting of concentric spaced shells B and B. lhe construction of the centrally disposed rotating column and the manner of regulating the flow of air into and through the rab ble arms of the furnace is fully set forth in my Patent Number 1,506,942 concurrently filed herewith for Letters Patent onv an improved ore roasting furnace.

the brick work Within the furnace structure is arranged I a series of hearths disposed in superposed relation, the lowermost hearth 1 being attached to the central column and rotating therewith while the rabble arms 2 associated with said hearth are thrust through the shell of the co furnace structure and are stationary. All

of the remaining hearths are attached to the stationary furnace shell and the rabble arms associatedtherewith are attached to and carried by the centrally disposed rotating column. Of the series of superposed hearths with which are associated the rabble arms 4, the lowermost one of the series and which is designated as .3 is the one through the opening 5 of which thematerial undergoing 7 treatment drops onto the bottom hearth l and is rabbled outwardly over said hearth untll discharged through an annular opening 6 into an annular trough 7 wherein scrapers attached to the revolving hearth 1 carry the calcined material around until it is dropped through a discharge opening 9. A circular seal curtain 10 which is secured to and depends from the under face of the hearth 1 rotates or moves within a seal pot so 11, which, like the annular trough 7, is integral with the furnace shell and this seal pct 11 is filled with dust or similar material to prevent the flow or escape of air or gas to or from the interior of the furnace. Air for maintaining cool the rabble arms 2, is introduced therein through an air supply pipe 12 and which air, after eflectin the cooling of the rabble arms by a circu ation theret rough, escapes therefrom through the outlet duct 13, the air inlet pipe 12 being attached or held to the stationary rabble alninls 2 by a bracket 14 secured to the furnace Air for combustion enters the furnace structure through the air inlet duct 15 and passes therefrom into the annular passageway 16, which completely surrounds the space between the lowermost hearth 1 and the hearth 3' next immediately above, which 1m) space is commonly known as the primary combustion chamber. The annular assage 16 is separated from the primary com ustion chamber by a curtain wall 17 and from the 'furnace shell by the insulated-lining 18. )5

Suitable burners '19 adapted to convey liquid, pulverized or aseous fuels, are thrust through the furnace shell and the insu lated lining 18, preferably at three points and in a semi-tangential. direction with no reference to the furnace shell. These bumers discharge into the combustion chamber the bottom hearth 1, and the size or area of through the ports or openings 20, which establish communication between the annular passage 16 and the interior of the furnace. If all of the air necessary or required for completecombustion is taken into the openings 20 and which in reality constitute somewhat small mixing chambers, a very hot and intense flame will result.

Passages 21 communicate the annular space 16 with radial passages 22 formed in the brick work of the hearth 3 next above these passageways may be regulated by damper tiles 24:, each of said tiles being accessible from the outside of the furnace structure through doors 25. -'Ihe air passing through the passages 2 2 of the hearth 3 enters the furnace or rather the primary combustion chamber, through the ports 23, Where the said air mixes with the combustible gases, causing or producing a long flame to pass upwardly through the furnace. It will be understood that the size of the passages for the air through the,hearth 3 should have a suficient area in relation to the size of the openings 20 that at least onethird of the total air for combustion may enter through the ports 23 into the primary combustion chamber.

By manipulation of the tiles 24,, from entirely shut to entirely open, the flame can be changed from a short and intensely hot one to a longer, less intensely hot and with a secondary combustion in ports 5, which will project a long flame further up into the furnace.

While I have described the invention in its preferred embodiment, I do not wish to v be understood as limiting or restricting the invention to the details of construction herein shown and described, but on the contrary wish to be understood as claiming the invention as broadly as the state of the art will warrant.

I claim- 1. In a multiple hearth mechanically rabbled furnace, a primary combustion chamber therein bounded top and bottom by two successive hearths, radially disposed air passages formed through the upper hearth and communicating at their inner end portions with the combustion chamber, an annular air passageway surrounding the combustion chamber and in communication with the air passages of the upper hearth, means for regulating the flow of air from .the said annular passageway into and through the radially disposed air passages of said hearth, fuel burners associated with the combustion chamber, and means for admitting air from the annular air passageway into the combustion chamber for supporting combustion therein.

2. In a multiple hearth mechanically rabbled furnace, a combustion chamber boundmergers ed top and bottom by two successive hearths and surrounded by a curtain wall spaced from the inner wall ofthe furnace and coacting therewith to form a vertically extended annular air passageway, a series of radially extended air passages formed through the said upper hearth and communicating at their outer ends with the said annular passageway and at their inner end with the combustion chamber, means for regulating the flow of air from said annular passageway intoand through the said radially disposed air passages, and fuel burners associated with the combustion chamber of the furnace.

3. In multiple hearth mechanically rabbled furnace, a combustion chamber therein bounded top and bottom by two successive hearths, the upper of which is providedwith a series of radially extended air passages communicating at their inner ends with the combustion chamber, means for ad mitting air through said air passages into the combustion chamber and fuel burners issociated with the said combustion cham= 4. In a multiple hearth mechanically rabbled furnace, a primary combustion chamber therein bounded top and bottom by two successive hearths, radially disposed air passages formed through the upper hearth and communicating at their inner end portions with the combustion chamber, an annular air passageway surrounding the comb netion chamber and in communication with the air passages of the upper hearth, fuel burners associated with the combustion chamber, and means for admitting air from the annular air passageway into the combustion chamber for supporting combustion therein.

5. In a multiple hearth mechanically rabbled furnace, a combustion chamber bounded top and bottom by two successive hearths and surrounded by a curtain wall spaced from the inner wall of the furnace and coacting therewith to form a vertically extended annular airpassageway, a series of radially extended air passages formed through the said upper hearth and communicating .at their outer ends with the said annular passageway and at their inner ends with the combustion chamber, and fuel burners associated with the combustionchamber of the furnace. v

6. In a multiple hearth mechanically rabbled calcining furnace, a stationary upper hearth, a rotating bottom hearth, stationary rabbling mechanism superimposed over said bottom hearth for agitating the material carried by the hearth and for gradually causing a movement thereof toward the 0 riphery of the hearth, means for projecting a calcining flame over said bottom hearth in a plane substantially parallel with its upper surface and at points between idle rabblin-g mechanism for acting on the material as conveyed by said hearth between said rabblingmechanism, an annular trough for receiving the material from the hearth, and provided with the discharge opening, and means operating in the trough for moving the material therein to discharge through said opening.

7. A calcining furnace including a stationary upper hearth and a rotating bottom hearth, stationary rabbling mechanism extending over the bottom hearth for conveying the material thereon toward the periphery of the hearth, means for projecting a calcining flame over said bottom hearth in a plane substantially parallel with its upper surface and at points between the rabbling mechanism for acting on the material as conveyed by said hearth between said rabbling mechanism, an annular trough beneath the bottom hearth for receiving the material therefrom, and provided with an outlet, scraper blades movable with the bottom hearth within said trough for conveying the material received therein to said dis- ,ae z'aeie i a superim osed over the bottom hearth;

means or injecting a calcining flame tangentially over the bottom hearth in a plane substantially parallel with the upper surface of the hearth and at points between the rabbling mechanism for acting on the material as conveyed between said rabbling mechanism, means for receiving the material as discharged peripherally of the hearth, an

annular sealing trough beneath the hearth,

an annular curtain depending from the hearth, and a sealing medium within the trough through which said curtain moves.

In testimony whereof l have signed my name to this specification.

ROBERT D. P1. 

